High battery voltage

[TOYTACO11]

What about while the engine is running? We need this data. Disconnect any accessories wired to the main battery and check voltage accross the terminals while engine is running.

12v is low for a healthy, charged battery at rest.
Shorted cells in a battery should cause voltage drop, rather than increased voltage, but who knows!?

If the alternator is overcharging, it is possible to have a residual surface charge for a short time. You can turn on the lights for a minute or two to dissipate surface voltage after shutting off the engine; but it doesn't seem like that is your issue.
Do you have any capacitors in your stereo or lighting systems?

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I said 12v wasnt the exact voltage I got the batteries are showing good 12.4-12.6v No capacitors that I know of…. It shouldnt have anything to do with the alternator when its not running…. When I key it off voltage goes to normal 12.4-6 as soon as I turn the key on the battery voltage rises between 15v-17v with engine off and with it running highest I saw was 15.4v

 

[TOYTACO11]

Are you checking the batteries disconnected? If they read lower when physically disconnected, it would point to some sort of issue with the isolator failing and running them in series somehow.

You nailed it thats is what was happening it had a bad ground cable and the isolator was doing some weird stuff all fixed now or at least it seems to be working now

 

[Marvelicious]

You nailed it thats is what was happening it had a bad ground cable and the isolator was doing some weird stuff all fixed now or at least it seems to be working now

Awesome, I'm glad I could help. When in doubt, suspect either the last thing you worked on, or the aftermarket part.

 

[LandLocked93]

You nailed it thats is what was happening it had a bad ground cable and the isolator was doing some weird stuff all fixed now or at least it seems to be working now

How all fixed now?

 

[TOYTACO11]

How all fixed now?

Its fixed now my guess is the dual battery isolator was tripping out due to a bad ground and trying to put the batteries in series… had no issues yesterday battery reading14.3 when running now

 

[LandLocked93]

Its fixed now my guess is the dual battery isolator was tripping out due to a bad ground and trying to put the batteries in series… had no issues yesterday battery reading14.3 when running now

Sooo...you pulled out the isolator out and wired the batts direct, or what specifically?

 

[TOYTACO11]

Sooo...you pulled out the isolator out and wired the batts direct, or what specifically?

Nope so I have a blue sea add a battery isolator that is wired in according to the directions and for my second battery ground Instead of running it to the other battery like. I probably should have I just grounded it to the body well that ground wire was not a good ground…

my guess is the isolator was reading the two batteries but was somehow trying to connect them into series or who knows what it was trying to do,

But it was trying to connect them and then it would hit the limits and kick off reason why the voltage would raise to over 17v then kick out.

All I did was run a seperate ground to my other battery connecting the two and moved the bad ground to a different spot and it all started working again…

Hope that explanation is understandable if not let me know and will try to clear it up some more